Hemispheric perception of emotional valence from facial expressions

The authors previously reported that normal subjects are better at discrimi nating happy from neutral faces when the happy face is located to the viewe r's right of the neutral face; conversely, discrimination of sad from neutr al faces is better when the sad face is shown to the left, supporting a rol e for the left hemisphere in processing positive valence and for the right hemisphere in processing negative valence. Here, the authors extend this sa me task to subjects with unilateral cerebral damage (31 right, 28 left). Su bjects with right damage performed worse when discriminating sad faces show n on the left, consistent with the prior findings. However, subjects with e ither left or right damage actually performed superior to normal controls w hen discriminating happy faces shown on the left. The authors suggest that perception of negative valence relies preferentially on the right hemispher e, whereas perception of positive valence relies on both left and right hem ispheres.